Hello Eric,
In the case you are using googlecharts, I think the best and easiest solution would be, to use the pivot functionality, combined with the row filters for pre pivot columns.
First you have to create the pivot in Chart Editor -> Table Configurator -> Table Pivots. Basically you just have to drag the column with the country names under your value column. This will create separate value columns for each country.
Then configure the chart for one of the countries. This will be your default chart, what will be displayed when you go to the view page.
Save the chart and add a new row filter. Now a dialog will pop up and asks for the column to be filtered. You should see the list of columns used in the chart, and some grayed out column names (these are the ones used for pivot). Select the one with the country names (it should be something like country (pre-pivot), then select simple category filter as type.
Save the charts and go to the view page. You should notice that a filter appeared, where you can select the country.
The list of the countries is always up to date, as it's generated runtime, so no problem when your data source is changed.
Note:
If you try to use this chart in a dashboard, this filter will not work.
I hope this will help you.
Cheers,
Zoli